Use of ledermycin compounds for inhibiting plant pathogenic fungi and preventing plant diseases

Abstract

The application of leidinmycin compounds in inhibiting plant pathogenic fungi and preventing and treating plant diseases belongs to the technical field of pesticide fungicides. In order to screen leidinmycin compounds capable of being used for preventing and treating plant diseases caused by plant pathogenic fungi or plant pathogenic oomycetes, five kinds of leidinmycin compounds are used for inhibiting plant pathogenic fungi and preventing and treating plant diseases. The leidinmycin compounds have strong inhibitory effect on plant pathogenic fungi, including the growth of fungal hyphae in Sclerotinia, Rhizoctonia, Elsinoe, Botrytis and Alternaria and the growth of oomycete hyphae in Pythium, Peronospora and Pseudomonas. In addition, the leidinmycin compounds have good prevention and treatment effect on plant diseases caused by the above plant pathogenic fungi and plant pathogenic oomycetes, and have no toxic side effect on plants, and can be developed and applied as effective components of pesticides or plant pathogenic fungicides.

Description

Technical Field

[0001] This invention belongs to the field of pesticide and fungicide technology, specifically relating to the application of lycorine compounds in inhibiting plant pathogens and controlling plant diseases. Background Technology

[0002] With changes in climate and agricultural planting patterns, crop diseases are becoming increasingly frequent, seriously threatening the healthy development of agriculture. Pesticides are essential agricultural inputs and a crucial guarantee for increased grain production. Currently, there are many types of pesticides on the market, but regardless of the type, long-term, unreasonable, or excessive use inevitably leads to pesticide resistance in plant pathogens. Therefore, there is an urgent need for the development and creation of new pesticides. Lydicamycin was the first secondary metabolite isolated from Streptomyces lydicus 2249-S3. Subsequently, Furumai T et al. isolated structural analogs of lydicamycin, TPU-0037-A, B, C, and D, from Streptomyces sp. TP-A0598. These compounds showed some inhibitory activity against Gram-positive bacteria such as Staphylococccus aureus, Bacillus subtilis, and Micrococcus luteus, but had no inhibitory effect on Gram-negative bacteria and yeast (Furumai T, Eto K, Sasaki T, et al. TPU-0037-A, B, C and D, novel lydicamycin congeners with anti-MRSA activity from Streptomyces platensis TP-A0598. [J]. Journal). of Antibiotics, 2002, 55(10):873. DOI:10.1002 / chin.200312203.). To date, no studies have been reported on the inhibitory effects of lycorine compounds on plant pathogenic fungi and oomycetes. Therefore, it would be of great significance to screen for compounds among lycorine compounds that can be used to control plant diseases caused by plant pathogenic fungi or oomycetes. Summary of the Invention

[0003] In order to screen for lycorine compounds that can be used to control plant diseases caused by plant pathogenic fungi or plant pathogenic oomycetes, this invention provides the application of lycorine compounds in inhibiting plant pathogens and controlling plant diseases. The specific technical solution is as follows:

[0004] The first objective of this invention is to provide the application of lidimycin compounds in inhibiting the mycelial growth of plant pathogenic fungi, including fungi of the genera *Sclerotinia* sp., *Rhizoctonia* sp., *Colletotrichum* sp., *Botrytis* sp., and *Alternaria* sp.;

[0005] The lidimycin class of compounds is any one of A)-E):

[0006] A) The structural formula is as shown in Formula I, R1 = CH3, R2 = OH;

[0007] B) The structural formula is as shown in Formula I, R1 = H, R2 = OH;

[0008] C) The structural formula is as shown in Formula I, R1 = H, R2 = H;

[0009] D) The structural formula is as shown in Formula I, R1 = CH3, R2 = H;

[0010] E) The structural formula is as shown in Formula II;

[0011]

[0012] In one embodiment of the present invention, the plant pathogenic fungus is any one of the following: *Sclerotinia sclerotiorum* (soybean or rapeseed sclerotinia sclerotiorum), *Alternaria tenuissima*, *Alternaria alternata*, *Rhizoctonia solani* (rice sheath blight), *Colletotrichum orbiculare* (cucumber anthracnose), and *Botrytis cinerea* (tomato gray mold).

[0013] A second objective of this invention is to provide the application of lidimycin compounds in inhibiting the mycelial growth of plant pathogenic oomycetes, including oomycetes from the genera *Phytophthora*, *Peronospora*, and *Pythium*; wherein the lidimycin compound is any one of A)-E).

[0014] A) The structural formula is as shown in Formula I above, R1 = CH3, R2 = OH;

[0015] B) The structural formula is as shown in Formula I above, R1 = H, R2 = OH;

[0016] C) The structural formula is as shown in formula I above, R1 = H, R2 = H;

[0017] D) The structural formula is as shown in formula I above, R1 = CH3, R2 = H;

[0018] E) The structural formula is as shown in formula II above.

[0019] In one embodiment of the present invention, the plant pathogenic oomycete is any one of Phytophthorainfestans, Phytophthora capsici, Phytophthora sojae, Pythium ultimum, Phytophthora nicotianae, Peronophthora litchi, and Pythium aphanidermatum.

[0020] The third objective of this invention is to provide the application of lidimycin compounds in the control of plant diseases caused by plant pathogenic fungi or plant pathogenic oomycetes; the plant pathogenic fungi include fungi from the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the plant pathogenic oomycetes include oomycetes from the genera *Phytophthora*, *Peronospora*, and *Pythium*; and the lidimycin compound is any one of A)-E).

[0021] A) The structural formula is as shown in Formula I above, R1 = CH3, R2 = OH;

[0022] B) The structural formula is as shown in Formula I above, R1 = H, R2 = OH;

[0023] C) The structural formula is as shown in formula I above, R1 = H, R2 = H;

[0024] D) The structural formula is as shown in formula I above, R1 = CH3, R2 = H;

[0025] E) The structural formula is as shown in formula II above.

[0026] In one embodiment of the present invention, the plant pathogenic fungus is any one of the following: *Sclerotinia sclerotiniae* of soybean or rapeseed, *Alternaria alternata*, *Alternaria alternata*, *Rhizoctonia solani*, *Anthracnose fungus* of cucumber, and *Gray mold fungus* of tomato.

[0027] In one embodiment of the present invention, the plant pathogenic oomycete is any one of Phytophthora indicum, Phytophthora capsici, Phytophthora sacchari, Pythium cerevisiae, Pythium tsao-ko, Pythium sacchari, Pythium lychee, and Pythium cucurbita.

[0028] A fourth object of the present invention is to provide a pesticide containing a lidecyn-type compound; said lidecyn-type compound is any one of A)-E):

[0029] A) The structural formula is as shown in Formula I above, R1 = CH3, R2 = OH;

[0030] B) The structural formula is as shown in Formula I above, R1 = H, R2 = OH;

[0031] C) The structural formula is as shown in formula I above, R1 = H, R2 = H;

[0032] D) The structural formula is as shown in formula I above, R1 = CH3, R2 = H;

[0033] E) The structural formula is as shown in formula II above.

[0034] The fifth object of this invention is to provide the application of lidimycin compounds in the preparation of pesticides for the control of plant diseases caused by plant pathogenic fungi or plant pathogenic oomycetes; the plant pathogenic fungi include fungi of the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the plant pathogenic oomycetes include oomycetes of the genera *Phytophthora*, *Peronospora*, and *Pythium*; and the lidimycin compound is any one of A)-E).

[0035] A) The structural formula is as shown in Formula I above, R1 = CH3, R2 = OH;

[0036] B) The structural formula is as shown in Formula I above, R1 = H, R2 = OH;

[0037] C) The structural formula is as shown in formula I above, R1 = H, R2 = H;

[0038] D) The structural formula is as shown in formula I above, R1 = CH3, R2 = H;

[0039] E) The structural formula is as shown in formula II above.

[0040] Furthermore, the pesticide also contains agriculturally acceptable adjuvants.

[0041] Furthermore, the application method of the pesticide is one or any combination of two or more of the following: spraying, seed soaking, coating, and root irrigation.

[0042] The sixth object of this invention is to provide the use of lidimycin compounds in the preparation of fungicides for inhibiting plant pathogenic fungi or plant pathogenic oomycetes, wherein the plant pathogenic fungi include fungi of the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; and the plant pathogenic oomycetes include oomycetes of the genera *Phytophthora*, *Peronospora*, and *Pythium*. The lidimycin compound is any one of A)-E).

[0043] A) The structural formula is as shown in Formula I above, R1 = CH3, R2 = OH;

[0044] B) The structural formula is as shown in Formula I above, R1 = H, R2 = OH;

[0045] C) The structural formula is as shown in formula I above, R1 = H, R2 = H;

[0046] D) The structural formula is as shown in formula I above, R1 = CH3, R2 = H;

[0047] E) The structural formula is as shown in formula II above.

[0048] The beneficial effects of this invention are:

[0049] The lydimycin compounds of this invention exhibit strong inhibitory effects against plant pathogenic fungi and oomycetes, including the ability to inhibit the growth of fungal hyphae in *Sclerotinia*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*, as well as the growth of oomycete hyphae in *Phytophthora*, *Peronospora*, and *Pythium*. Furthermore, the lydimycin compounds of this invention demonstrate good control effects against plant diseases caused by the aforementioned plant pathogenic fungi and oomycetes, and have no toxic side effects on plants. They can be developed and applied as effective components in pesticides or fungicides for plant pathogens. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0051] The lidimycin compounds used in this invention are any one of A)-E):

[0052] A) The structural formula is as shown in Formula I, R1 = CH3, R2 = OH;

[0053] B) The structural formula is as shown in Formula I, R1 = H, R2 = OH;

[0054] C) The structural formula is as shown in Formula I, R1 = H, R2 = H;

[0055] D) The structural formula is as shown in Formula I, R1 = CH3, R2 = H;

[0056] E) The structural formula is as shown in Formula II;

[0057]

[0058] The plant pathogenic fungi used in this invention, namely *Sclerotinias clerotiorum* (soybean or rapeseed sclerotium rot pathogen), *Alternaria tenuissima* (alternaria tenuissima), *Alternaria alternata* (alternaria alternata), *Rhizoctonia solani* (rice sheath blight pathogen), *Colletotrichum orbiculare* (cucumber anthracnose pathogen), and *Botrytis cinerea* (tomato gray mold pathogen), are preserved at Northeast Agricultural University.

[0059] The plant pathogenic oomycetes used in this invention, namely Phytophthora infestans, Phytophthora capsici, Phytophthora sojae, Pythium ultimum, Phytophthora nicotianae, Peronophthora litchi, and Pythium aphanidermatum, are preserved at Northeast Agricultural University.

[0060] The preparation method of the V8 solid culture medium used in this invention is as follows:

[0061] Add 3.4g of calcium carbonate powder to 340mL of V8 mixed fruit and vegetable juice, centrifuge at 4℃ and 4000rpm for 5min, measure 300mL of the fruit and vegetable juice without solid suspension, add 2700mL of deionized water to prepare 3L of V8 liquid culture medium, add 48g of agar powder, mix well, dispense, sterilize at 121℃ for 30min, and store at room temperature (the V8 mixed fruit and vegetable juice was purchased from the United States and is a 340mL can of "Kampo V8 Vegetable Juice 100%" standard).

[0062] Example 1: Application of lidimycin compounds in inhibiting the mycelial growth of plant pathogenic fungi

[0063] The mycelial growth rate method was used to determine the toxicity of various fungi in the laboratory. Lidecycin A, Lidecycin B, Lidecycin C, Lidecycin D, Lidecycin E, and control drugs (cyhalothrin, azoxystrobin, and carbendazim) were prepared as 10 mg / ml stock solutions in methanol and stored at 4℃. During the experiment, the drug solutions were diluted with methanol to 0.4 mg / ml, and then corresponding volumes were added to PDA agar plates to achieve final drug concentrations of 0.2 μg / ml, 0.4 μg / ml, 0.6 μg / ml, 0.8 μg / ml, 1 μg / ml, 2 μg / ml, 4 μg / ml, and 8 μg / ml, respectively. PDA agar plates with an equal volume of methanol were used as controls. Holes were punched at the edge of the fungal colonies, and the mycelial cakes were inoculated into the PDA agar plates with the mycelial side down. The plates were sealed and incubated upside down in a 28℃ incubator for 5-6 days. When the hyphae in the control plate grew to two-thirds of the plate diameter, the colony diameter was measured using the cross-cross method. The hyphal inhibition effects of lydicamycin-like compounds and control drugs on the pathogens of sclerotinia rot of soybean or rapeseed, Alternaria alternata, Alternaria alternata, the pathogen of rice sheath blight, the pathogen of cucumber anthracnose, and the pathogen of tomato gray mold were calculated. SPSS software was used to calculate the toxicity regression equations and median inhibitory concentrations (EC50) of lydicamycin-like compounds and control drugs on fungi such as sclerotinia rot of soybean.

[0064] The experimental results are shown in Table 1. Analysis of the experimental results in Table 1 shows that lidimycin compounds have a good inhibitory effect on the mycelial growth of *Sclerotinia sclerotiorum*, *Alternaria alternata*, *Alternaria alternata*, *Rhizoctonia solani*, *Anthracnose*, and *Gray mold* of tomatoes. The inhibitory concentration (EC50) is comparable to that of the control agent, indicating that the inhibitory effect of lidimycin compounds on the mycelial growth of the above fungi is comparable to that of the control agent.

[0065] Table 1. Inhibitory effect of lidimycin AE on plant pathogenic fungi.

[0066]

[0067] Note: "-" indicates that it has not been tested.

[0068] Example 2: Application of lidimycin-like compounds in inhibiting the mycelial growth of plant pathogenic oomycetes

[0069] The mycelial growth rate method was used to determine the toxicity of various oomycetes in the laboratory. Lidecycin A, Lidecycin B, Lidecycin C, Lidecycin D, Lidecycin E, and the control drug (Methamphetamine) were prepared as 10 mg / ml stock solutions in methanol and stored at 4℃. During the experiment, the drug solutions were diluted with methanol to 0.4 mg / ml, and then corresponding volumes were added to V8 agar plates to achieve final drug concentrations of 0.2 μg / ml, 0.4 μg / ml, 0.6 μg / ml, 0.8 μg / ml, 1 μg / ml, 2 μg / ml, 4 μg / ml, and 8 μg / ml, respectively. V8 agar plates with an equal volume of methanol were used as controls. Holes were punched at the edge of the colonies of each oomycete, and the mycelial cakes were inoculated into the V8 agar plates with the mycelial side down. The plates were sealed and incubated upside down in a 28℃ incubator for 5-6 days. When the mycelial diameter in the control plate reached two-thirds of the plate diameter, the colony diameter was measured using the cross-cross method. The inhibitory effects of lidecycin compounds and metalaxyl on the mycelia of Phytophthora virulence, Phytophthora capsici, Phytophthora sacchariformis, Pythium cerevisiae, Phytophthora tsacchariformis, Pythium tsacchariformis, Pythium tsacchariformis, and Pythium tsacchariformis were calculated. SPSS software was used to calculate the virulence regression equation and median inhibitory concentration (EC50) of lidecycin compounds and metalaxyl on Phytophthora sacchariformis and other oomycetes.

[0070] The experimental results are shown in Table 2. Analysis of the experimental results in Table 2 shows that lidimycin compounds have a good inhibitory effect on the mycelial growth of oomycetes such as Phytophthora soybeana, Phytophthora capsici, and Phytophthora pathogenica. The inhibitory concentration, i.e., the EC50 value, is comparable to that of metalaxyl, indicating that the inhibitory effect of lidimycin compounds on the mycelial growth of oomycetes such as Phytophthora soybeana, Phytophthora capsici, and Phytophthora pathogenica is comparable to that of metalaxyl.

[0071] Table 2. Inhibitory effect of lidimycin AE on plant pathogenic oomycetes

[0072]

[0073] Example 3: Application of lycormycin compounds in the control of plant fungal diseases

[0074] (1) Application of lidimycin compounds in the control of tomato gray mold

[0075] Using a small sprayer, evenly spray the prepared fungicide (100 μg / mL) onto three uniformly sized, healthy tomato seedlings (control fungicide was boscalid), and place them in a cool, well-ventilated area to air dry naturally. Rinse the tomato gray mold pathogen cultured for 2 weeks with sterile water, filter through four layers of gauze, and prepare 10... 5Prepare a spore suspension of 1 spore / ml. 24 hours after spraying the pesticide, evenly spray the spore suspension onto the tomato seedlings. Place the treated seedlings in a sealed plastic rack and incubate at 26℃. Water daily and observe for disease development. Once the disease becomes severe, record the disease status according to the following grading method:

[0076] Each treatment recorded 30 leaves. Grade 0: No lesions; Grade 1: Lesion area ≤ 5% on leaves; Grade 3: 5% < lesion area ≤ 15% on leaves; Grade 5: 15% < lesion area ≤ 25% on leaves; Grade 7: 25% < lesion area ≤ 50% on leaves; Grade 9: Lesion area > 50% on leaves.

[0077] The disease index and control effect are calculated based on the affected area of ​​leaves, and then the control effect is statistically analyzed.

[0078] The formulas for calculating the disease index and control efficacy in detached leaves are as follows:

[0079]

[0080]

[0081] The results are shown in Table 3. The control efficacy of 100 μg / mL lidimycin A and lidimycin B against tomato gray mold was 68.2% and 71.5%, respectively, which was slightly better than the control efficacy of the same concentration of the control drug cyazofamid (63.1%).

[0082] (2) Application of lidimycin compounds in the prevention and control of sclerotinia stem rot in rapeseed

[0083] Select healthy rapeseed plants with 2-3 true leaves. The pesticide concentration was 100 μg / mL, with boscalid as the control pesticide and sterile water as the blank control. Select rapeseed plants of uniform size and leaf size, and spray the pesticide evenly onto the rapeseed leaves. Allow them to air dry indoors overnight. Then, place a 5 mm diameter mycelial cake of rapeseed sclerotinia pathogen of the same age in the center of each leaf, with the mycelial side facing down. After inoculation, incubate the rapeseed in an environment of 24℃ and relative humidity greater than 80% for 5 days. The disease incidence in the blank control was graded according to the following criteria:

[0084] Grade 0: No symptoms appear; Grade 1: Lesion area on leaves ≤ 5%; Grade 3: Lesion area on leaves ≤ 10% (6% <); Grade 5: Lesion area on leaves ≤ 20% (10% <); Grade 7: Lesion area on leaves ≤ 40% (20% <); Grade 9: Lesion area on leaves > 40%.

[0085] The disease index and control effect are calculated based on the affected area of ​​leaves, and then the control effect is statistically analyzed.

[0086] The formulas for calculating the disease index and control efficacy in detached leaves are as follows:

[0087]

[0088]

[0089] The results are shown in Table 3. The control efficacy of 100 μg / mL lidimycin A and lidimycin B against sclerotinia stem rot in rapeseed was 82.5% and 87.1%, respectively, which was better than the control efficacy of the same concentration of the control drug cyazofamid (52.3%).

[0090] (3) Application of lidimycin compounds in the prevention and control of cucumber anthracnose

[0091] The pesticide concentration was 100 μg / mL, with carbendazim as the control and sterile water as the blank control. Sensitive cucumber varieties were selected for planting. Once the cucumbers had two cotyledons, leaves from the same location, with consistent growth and 1-2 cm petioles were cut. The petioles were wrapped with damp cotton balls and placed in petri dishes, back side up, to maintain humidity. The prepared pesticide was evenly sprayed onto the back of the leaves, and the solution was allowed to air dry naturally. Inoculation was performed 24 hours later. Before inoculation, a sterilized inoculation needle was used to pierce an infection area approximately 4 mm in diameter on the surface of the cucumber leaves to facilitate infection by the cucumber anthracnose fungus. After inoculation, the dishes were covered and placed in an artificial climate chamber at 24℃ and relative humidity above 90%, with alternating light / dark cycles of 12 hours daily. Results were assessed after 7 days. Based on the disease incidence in the blank control, the diameter of lesions was measured and recorded using the cross-sectional method. The control effect was calculated using the following formula:

[0092] Lesion diameter (mm) = Measured lesion diameter - 4 (mushroom cake diameter)

[0093]

[0094] The results are shown in Table 3. The control efficacy of 100 μg / mL lidimycin A and lidimycin B against cucumber anthracnose was 70.5% and 68.7%, respectively, which was comparable to the control efficacy of the same concentration of carbendazim (76.1%).

[0095] (4) Application of lidimycin compounds in the control of rice sheath blight

[0096] The pesticide concentration was 100 μg / mL, with azoxystrobin as the control pesticide and sterile water as the blank control. 10 cm sections of rice leaves were neatly cut and soaked in different concentrations of pesticide for 10 minutes each, then removed and air-dried. Fungal cakes were extracted from a PDA plate containing rice sheath blight pathogen using a 0.5 cm diameter punch and placed in the center of the leaf. The rice leaves were then placed in a constant temperature and light incubator (25±2℃, 12h light / dark alternation, 80% relative humidity). After 5 days, the length of the lesion on each leaf was measured, and the control effect was calculated using the following formula:

[0097]

[0098] The results are shown in Table 3. The control efficacy of 100 μg / mL lidecycin A and lidecycin B against rice sheath blight was 87.8% and 80.2%, respectively, which was comparable to the control efficacy of the same concentration of the control drug azoxystrobin (88.7%).

[0099] (5) Application of lidimycin compounds in the prevention and control of tobacco red spot disease

[0100] The pesticide concentration was 100 μg / mL, with boscalid as the control pesticide and sterile water as the blank control. 40-day-old tobacco plants were selected, and the leaves were sprayed with the pesticide at a rate of 50 ml per plant. 24 hours after spraying, the 4th and 5th leaves were selected and treated using the spore suspension injection method (10 μg / mL). 6 Inoculate with *Alternaria alternata* (number of cells / ml). After 3 days of incubation at 28℃ with humidity, observe leaf disease development. Disease grading standards are as follows:

[0101] Grade 0: No symptoms appear; Grade 1: Lesion area on leaves ≤1%; Grade 3: 2% < lesion area on leaves ≤5%; Grade 5: 5% < lesion area on leaves ≤10%; Grade 7: 10% < lesion area on leaves ≤20%; Grade 9: Lesion area on leaves >20%.

[0102] Based on the affected area of ​​leaves, the disease index and control effect are calculated, and then the control effect is statistically analyzed.

[0103] The formulas for calculating the disease index and control efficacy in detached leaves are as follows:

[0104]

[0105]

[0106] The results are shown in Table 3. The control efficacy of 100 μg / mL lidimycin A and lidimycin B against tobacco red spot disease was 67.5% and 58.9%, respectively, which was comparable to the control efficacy of the same concentration of the control drug cyazofamid (62.1%).

[0107] Table 3. Control effects of lidimycin A and lidimycin B on plant fungal diseases.

[0108]

[0109]

[0110] Note: "-" indicates that it has not been tested.

[0111] Example 4: Application of lycormycin compounds in the control of oomycete diseases in plants

[0112] Leaves of similar size from peppers, soybeans, tomatoes, tobacco, or potatoes at the same growth stage were collected, cleaned, disinfected with 5% sodium hypochlorite for 5 minutes, and then rinsed three times with sterile distilled water. A 60 μg / mL solution of lidecycin A, lidecycin B, and a control drug was prepared and sprayed onto the leaves. Distilled water was used as a control, with a spraying rate of 100 μl per leaf. For protective effects, the solution was sprayed onto the leaves first, followed by inoculation with 5 mm of pathogenic fungal discs 12 hours later. For curative effects, 5 mm of pathogenic fungal discs were inoculated onto the leaves first, followed by spraying with the solution 12 hours later. Potato leaves were inoculated with *Phytophthora indicum*, and pepper leaves were inoculated with *Phytophthora capsici*. Pepper leaves were incubated at 28°C under light for 5 days, and potato leaves were incubated at 20°C under light for 5 days. Disease index was recorded, and the control effect was calculated.

[0113] Disease index: Based on the area of ​​leaf lesions, the disease index is divided into four levels from 0 to 4: Level 0: no symptoms, Level 1: 1-25%, Level 2: 26-50%, Level 3: 51-75%, Level 4: 76-100%.

[0114] The formulas for calculating the disease index and prevention and control effectiveness are as follows:

[0115]

[0116]

[0117] The experimental results are shown in Table 4. As can be seen from the table, lidecycin A and lidecycin B have good control efficacy against Phytophthora in potato leaves, and their control effect is better than that of metalaxyl. Lidecycin A and lidecycin B have good control efficacy against Phytophthora capsici in pepper leaves, and their control effect is better than that of metalaxyl.

[0118] Table 4. Control effects of lidecyn A and B on potato late blight and pepper blight.

[0119]

[0120] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the claims.

Claims

1. The application of lidimycin compounds in inhibiting the mycelial growth of plant pathogenic fungi, characterized in that, The plant pathogenic fungi include fungi belonging to the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the lidimycin-like compound is any one of A)-E). A) The structural formula is as shown in Formula I, R1=CH3, R2=OH; B) The structural formula is as shown in Formula I, R1=H, R2=OH; C) The structural formula is as shown in Formula I, R1=H, R2=H; D) The structural formula is as shown in Formula I, R1=CH3, R2=H; E) The structural formula is as shown in Formula II; Equation I; Formula II.

2. The application according to claim 1, characterized in that, The plant pathogenic fungus is any one of the following: *Sclerotinia sclerotiorum* of soybean or rapeseed, *Alternaria alternata*, *Alternaria alternata*, *Rhizoctonia solani*, *Anthracnose* of cucumber, and *Gray mold* of tomato.

3. The application of the lycorine compound as described in claim 1 in inhibiting the mycelial growth of plant pathogenic oomycetes, characterized in that, The plant pathogenic oomycetes include oomycetes from the genera Phytophthora, Peronospora, and Pythium.

4. The application according to claim 3, characterized in that, The plant pathogenic oomycete is any one of Phytophthora indicum, Phytophthora capsici, Phytophthora sacchari, Pythium cerevisiae, Pythium tsici, Pythium sacchari, Pythium lychee, and Pythium cucurbita.

5. The application of the lycormycin-like compounds described in claim 1 in the prevention and control of plant diseases, characterized in that, The plant diseases are caused by plant pathogenic fungi or plant pathogenic oomycetes; the plant pathogenic fungi include fungi from the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the plant pathogenic oomycetes include oomycetes from the genera *Phytophthora*, *Peronospora*, and *Pythium*.

6. The application according to claim 5, characterized in that, The plant pathogenic fungus is any one of the following: *Sclerotinia sclerotiorum* of soybean or rapeseed, *Alternaria alternata*, *Alternaria alternata*, *Rhizoctonia solani*, *Anthracnose* of cucumber, and *Gray mold* of tomato.

7. The application according to claim 5, characterized in that, The plant pathogenic oomycete is any one of Phytophthora indicum, Phytophthora capsici, Phytophthora sacchari, Pythium cerevisiae, Pythium tsici, Pythium sacchari, Pythium lychee, and Pythium cucurbita.

8. The use of the lidimycin-like compound as described in claim 1 in the preparation of pesticides for the control of plant diseases, characterized in that, The plant diseases are caused by plant pathogenic fungi or plant pathogenic oomycetes; the plant pathogenic fungi include fungi from the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the plant pathogenic oomycetes include oomycetes from the genera *Phytophthora*, *Peronospora*, and *Pythium*.

9. The use of the lidimycin-like compound of claim 1 in the preparation of a fungicide for inhibiting plant pathogenic fungi or plant pathogenic oomycetes, characterized in that, The plant pathogenic fungi include fungi from the genera *Sclerotium*, *Rhizoctonia*, *Colletotrichum*, *Botrytis*, and *Alternaria*; the plant pathogenic oomycetes include oomycetes from the genera *Phytophthora*, *Peronospora*, and *Pythium*.

Images